EUV Masks

doi:10.1117/3.2581446.ch4

EUV Masks

Book: Extreme Ultraviolet Lithography

Author(s): Harry J. Levinson

Published: 2020

https://doi.org/10.1117/3.2581446.ch4

Abstract

As discussed previously, there are no high-transmission optical materials at EUV wavelengths due to limitations imposed by atomic absorption. As a consequence, all optical elements in the lens must be reflective for EUV lithography. Similarly, EUV masks must be either reflective or stencil-type. The semiconductor industry has made reflective masks standard, as they were seen as more practical than stencil masks. This means that masks for EUV lithography are fundamentally different from those used for optical lithography. An extensive amount of engineering effort was directed at determining what the format should be for reflective EUV masks, and additional effort was required to make them suitable for use in high-volume manufacturing.